Electrical heating apparatus, in particular underfloor heating

ABSTRACT

An electrical heating apparatus comprises a heating conductor device having at least one heating circuit with at least one power stage, a heating temperature setting unit that sets a set-point temperature, a temperature sensor that measures an actual temperature, an activating device that activates the heating conductor device on the basis of the respective values of the set-point and actual temperatures, a first energy source and a single control apparatus with a control module, which is connected between the first energy source and the heating conductor device. Further, the heating temperature setting unit and the temperature sensor output their signals to the control apparatus. The control module activates or deactivates first, second and/or additional more power stages individually or in combination on the basis of the difference between the set-point and actual values.

FIELD OF THE INVENTION

The present invention relates to an electrical heating apparatus, in particular underfloor heating, which is connectable to a first electrical energy source, having a heating conductor device, with a first heating circuit and a first power stage, at least one second heating circuit with a second power stage and/or further heating circuits with further power stages, a heating temperature setting unit for setting the set-point temperature, a temperature sensor for measuring the actual temperature, a device for activating the heating conductor device on the basis of the respective values of the set-point and actual temperatures.

BACKGROUND OF THE INVENTION

In addition to heating systems which are connected to the hot water, electrically operated surface heating apparatus are also used. In this connection, resistor cables with an incorporated heating conductor are laid under, in or on the floor screed. Owing to the low construction height, such electrical heating conductor devices can be laid directly under floor coverings. Owing to the relatively small diameter of the heating cables, these can be laid in the adhesive bed of tiles and even used under laminate flooring. When a voltage is applied to the heating conductors, these generate heat. A control device which is connected to sensors to detect the ambient temperature controls the heating operation by a voltage being applied to the heating conductors when a predefined temperature is undershot, wherein the voltage ceases to be applied once the predefined temperature has been exceeded. As soon as the predefined temperature is undershot again, the heating conductor is activated once more.

An electrical surface heating apparatus of the type mentioned at the outset is known from EP 2 530 389 A2. That document relates to an electrical surface heating apparatus for internal and/or external use, in particular underfloor heating having a heating conductor device with at least one cold connection region to an electrically conducting insulated connection line and a heating conductor region with a heating element having an electrically conducting insulated heating conductor which outputs a largely fixed heating power when voltage is applied, a switching device for switching on or off the voltage applied to the heating conductor, a control device for operating the heating conductor device to achieve a desired set ambient temperature and a connection device for the heating conductor device for connecting to a voltage source, wherein said electrical heating apparatus is distinguished in that the heating element has at least two or more heating conductors and the switching device is designed such that each heating conductor can have voltage applied to it separately, with the result that the heating conductors can have voltage applied thereto individually or combined in a predefined number or together at the same time during a predefined time interval. Such a surface heating apparatus can be operated in an energy-saving manner, variably adapted in each case to the respective temperature ratios, produced economically and laid using common laying techniques.

Furthermore, a surface heating apparatus is known in which heating conductors with different resistance values and hence power values are used, wherein each heating wire can be separately controlled. In this case, a central thermostat is used which controls a heating power stage and by means of which a floor temperature can be set. In addition, yet further individual thermostats are present which can be activated separately and which activate further power stages within the heating conductor. However, a heating apparatus such as this has poor energy efficiency, is expensive and is less user-friendly.

SUMMARY OF THE INVENTION

Proceeding from the stated prior art, the object or the technical problem on which the invention is based is to specify an electrical heating apparatus of the type mentioned at the outset which keeps the advantages stated in the prior art and, moreover, has improved energy efficiency and thus ensures economical heating which can be laid by means of the simple and proven laying techniques, which can be produced economically and which ensures a permanently reliable function. A further object consists in connecting alternative energy sources in the case of heating apparatus of the type mentioned at the outset and, at the same time, in addition to simple assembly, enabling high energy efficiency, ensuring economical application, being variably adjustable and enabling a permanently reliable functionality.

The electrical heating apparatus according to the invention of the type mentioned at the outset is accordingly distinguished in that a single control apparatus with a control module is present and is designed as a multistage controller and is connected between the first energy source and the heating device, wherein the heating temperature setting unit and the temperature sensor output their signals to the control apparatus and the control module activates or deactivates one or more power stages of the heating circuits individually or in combination on the basis of the difference between the set-point and actual values.

Owing to the fact that a single control apparatus is used for all of the heating circuits, the elaborate, expensive and user-unfriendly installation of a plurality of thermometers as in the prior art is avoided and the overall heating apparatus has high energy efficiency.

A particularly preferred configuration of the heating apparatus according to the invention is distinguished in that the control module is designed as a PI control module which calculates in each case a control output on the basis of the control deviation, that is to say the difference between set-point and actual temperature, the P component of said control output being dependent on the magnitude of the control deviation and the I component of said control output being dependent on the duration of the control deviation, and correspondingly actuates the individual heating circuits. By this type of control, the heating power is successively reduced as the set-point temperature is approached and thus overshooting of the floor temperature above the set-point value is avoided. This means an energy-saving and efficient conversion of the electrical energy and, in addition to the increase in comfort, also an improvement in economy on the part of the user.

The power stages of the heating circuits can in this case each have identical heating power or different heating powers. In particular, the latter variant is particularly effective in relation to the control characteristics of a PI control module and, has a result, has high efficiency.

A particularly advantageous development of the heating apparatus according to the invention which affords particularly great advantages in terms of the economic conversion of an energy concept is distinguished in that, in addition, a second electrical energy source for the power stages of the heating circuits is connectable to the control apparatus.

A particularly approved and effective advantageous configuration of the heating apparatus according to the invention is distinguished in that the first energy source is the usual power grid and the second energy source is designed as individual alternative energy source, for instance photovoltaic installation or wind turbine.

An embodiment which is particularly advantageous in terms of constructive conversion and ensures efficient control is distinguished in that a logic switching unit is connected between the second energy source and control apparatus and outputs to the control apparatus a control signal relating to the respective present energy production of the second energy source and, in the event of sufficient energy production, enables the second energy source to supply energy to the heating conductor device.

A particularly user-friendly variant embodiment which reliably ensures a permanently reliable functionality in the operating state is distinguished in that an operating mode switching unit is present which communicates with the control apparatus and by means of which the following operating states can be set via the control apparatus:

first state: energy supply to the heating conductor device with the power stages thereof via the first energy source, second state: energy supply to the heating conductor device with the power stages thereof via the second energy source, and third state: energy supply to the heating conductor device with the power stages thereof by a combination of the first and second energy source.

If the user decides to use only the alternative energy source for heating purposes, a particularly advantageous configuration of the heating apparatus according to the invention is distinguished in that the control apparatus is designed such that the heating conductor device is activated only when a positive signal of the logic unit is present and the second state is activated, otherwise the heating conductor device is deactivated.

A preferred development which increases user-friendliness and implements the safety regulations which are to be taken into account is distinguished in that a fourth operating state, frost protection, can be set by the operating mode switching unit, in which fourth operating state the control apparatus activates the heating conductor device when a predefined temperature is undershot, independently of the set operating state of the second energy source.

An advantageous configuration which is particularly simple to implement in terms of construction and also has recourse to production techniques which are approved in practice is distinguished in that the heating conductor device has a heating conductor which has a plurality of electrically insulated heating conductors which are actuable independently of one another and have identical or different power stages, which can be activated separately or in combination.

A configuration which is particularly advantageous in terms of implementing a surface heating apparatus is distinguished in that the heating conductor device with heating conductor is designed as one or more heating mats, wherein the heating conductors are present, in particular, in a meandrous arrangement.

A compact and user-friendly advantageous configuration is distinguished in that the control module, the heating temperature setting unit and operating mode setting unit are arranged in a controller housing.

An advantageous configuration which further increases the user-friendliness is distinguished in that the housing has optical display units for displaying the set set-point temperature and the set operating state.

A particularly advantageous configuration in practice which has very good control characteristics is distinguished in that two heating circuits are present, wherein the first power stage applies approximately 33% of the total heating power and the second power stage applies approximately 66% of the total heating power, wherein it has proven particularly advantageous for the control output characteristics to be designed such that, in the case of a control output, calculated by the control apparatus, of approximately 33%, the first power stage is activated, in the case of a control output of from approximately 33% to 66%, the second power stage is activated, and in the case of a control output between 66% and 100%, the first and second power stages are activated.

The heating apparatus according to the invention makes possible the use as electric heater which becomes a fundamental component in the energy mix owing to the energy use. This is, in particular, from the point of view that alternative energy sources are also used in a user-friendly and efficient way for the heating apparatus.

Owing to the use of a plurality of heating power circuits, an energy-saving heating operation by the control apparatus of the invention, which could not be implemented up to now, becomes possible. In addition, the safety is increased since the additional heating power circuits can be used as reserve heating circuits, with the result that a comfort heating operation can still be maintained in the event of a failure of a heating circuit. As a result, significant costs for time-consuming fault location and repair in the event of a breakdown of a heating power circuit can be avoided.

In particular, the following advantages result from the heating apparatus according to the invention:

-   -   An energy-saving operation is possible.     -   The thin heating systems known from the prior art which use the         known narrow, coupling-free connection techniques of the         applicant can be used without a problem.     -   By connecting and disconnecting individual heating conductors in         connection with the control apparatus, it is possible to achieve         a variable heating operation with efficient energy conversion, a         high degree of user-friendliness and permanently reliable         function.     -   In the event of a failure of an active heating circuit, the         connection of a reserve heating circuit is possible without a         problem, which considerably increases the heating operation         safety.

The control apparatus which is designed, according to a preferred exemplary embodiment, as a two-circuit controller, ensures a particularly energy-efficient usage.

In an exemplary embodiment, the desired floor temperature is set via a rotary knob and a sliding switch enables the selection of the operation mode. In addition to the basic function of underfloor heating with three heating stages (heating circuit 1, heating circuit 2, heating circuits 1+2), the control apparatus can be used particularly expediently in connection with alternative energy sources (for example photovoltaic installations or wind turbines) to optimize the intrinsic consumption.

In a preferred exemplary embodiment, three operating modes are freely selectable by the user:

1. Switched off (frost protection active). 2. Only operational in the case of sufficient energy supply by the alternative energy source. 3. Operation by the first and second energy source.

Depending on the present difference between set-point and actual value of the floor temperature, the control apparatus connects only the heating circuit 1, the heating circuit 2 or both heating circuits.

By the use of the logic unit for the photovoltaic installation, it is possible to achieve without a problem an efficient management of the current yield from said alternative energy source, which is used when necessary for heating purposes or the yield from which is fed into the power grid provided no requirements for the heating operation are present.

Further embodiments and advantages of the invention emerge from the features which are further cited in the claims and from the exemplary embodiments specified below. The features of the claims may be combined with one another in any way, provided they is not obviously mutually exclusive.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and advantageous embodiments and developments of said invention are described and explained in more detail below on the basis of the examples illustrated in the drawing. The features which can be gathered from the description and the drawing can be applied individually per se or multiply in any combination according to the invention. In the drawing:

FIG. 1 shows a highly schematic illustration of an electrical heating apparatus with a plurality of heating circuits which are controlled by a control apparatus, wherein a first energy source and a second energy source are connected to the control apparatus via a distributor,

FIG. 2 shows a highly schematic illustration of an electrical heating apparatus with a plurality of heating circuits which are controlled by a control apparatus, wherein a first energy source and a second energy source are separately connected to the control apparatus,

FIG. 3 shows a highly schematic illustration of a heating apparatus with a plurality of heating circuits and a control apparatus which controls the heating circuits separately or in combination, wherein the control apparatus is communicatively connected to a first energy source,

FIG. 4 shows a highly schematic illustration of a heating apparatus with a plurality of heating circuits and a control apparatus which controls the heating circuits separately or in combination, wherein the control apparatus is communicatively connected to a first and a second energy source via a distributor, and

FIG. 5 shows a highly schematic illustration of an electrical heating apparatus with two heating circuits which are controlled via a two-circuit controller and the power for which is drawn from the power grid and/or a photovoltaic installation with intermediate connection of a distributor unit and a logic unit connected downstream of the photovoltaic installation.

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the Invention

FIG. 1 illustrates highly schematically a simplified block diagram of an electrical heating apparatus 10 which has a heating conductor device 12 with three heating circuits 14.1, 14.2, 14.3 with in each case associated power stages L1, L2, L3. The heating conductor device 12 can in this case—as illustrated on the right of FIG. 1 in brackets—be designed as a heating mat which has a meandering heating conductor 13 within which the individual heating circuits 14.1, 14.2, 14.3 are present in an electrically insulated manner as individual heating wires. Such a heating conductor 13 is described in EP 2 530 389 from the applicant.

The individual heating circuits 14.1, 14.2, 14.3 are connected to a control apparatus 20 which, depending on requirements, activates the heating circuits 14.1, 14.2, 14.3 individually or in combination via relays.

A first energy source 16 and a second energy source 30 are connected to the control apparatus 20 via a distributor 36, which energy sources supply both the control apparatus 20 and the heating circuits 14.1, 14.2, 14.3 with electrical energy. In a practical application case, the first energy source 16 is the power grid which in general is available everywhere in a building, and the second energy source 30 is an individual alternative energy source, for instance a photovoltaic installation, wind turbine or the like, which is operated on site.

The control apparatus 20 can be set such that the energy supply can be operated only via the second, alternative energy source 30 or via the combination of the first energy source and second energy source 30.

FIG. 2 likewise illustrates highly schematically a block circuit diagram of an alternative electrical heating apparatus 10, which differs from the heating apparatus 10 according to FIG. 1 in that the first and second energy sources 16, 30 are separately connected to the control apparatus 20 and thus their energy can be drawn either completely separately or in combination. Identical components have identical reference signs and are not explained a second time.

FIG. 3 shows a block circuit diagram of a heating apparatus 10 in which only a first energy source 16 is connected to the control apparatus 20 via a first connection unit 17. The control apparatus 20 also has three connection outputs 21 to which the heating circuits 14.1, 14.2, 14.3 of the heating device 12 are each separately connected. Within the control apparatus 20, there is a control module 22 to which a signal of a heating temperature setting unit 24, which is present on the control apparatus 20, is applied. The signal of the heating temperature setting unit 24 represents the respectively desired set-point temperature.

Furthermore, a temperature sensor 18 is present, which is arranged in the region of the heating device 12 and which outputs a signal to the control module 22, which signal represents the actual temperature value.

Both the control module 22 and the heating circuits 14.1, 14.2, 14.3 are supplied with energy via the first energy source 16. In this case, the control module 22 is preferably designed as a PI control module. The control module 22 first calculates the difference between the set-point and actual temperatures, that is to say the control deviation, and then calculates a control output therefrom. The control output is dependent on the magnitude of the control deviation (P component) and the duration of the control deviation (I component). The greater this is and the longer it endures, the higher the control output is set. On the basis of the magnitude of the respective control output, the control module 22 activates the respective heating circuits 14.1, 14.2, 14.3, either individually or in combination.

By means of such a control apparatus 20 with the control module 22, an economical and efficient power supply is ensured, wherein the heating power is successively reduced as the set-point temperature is approached and thus overshooting of the floor temperature above the set-point temperature is avoided, which significantly increases the energy efficiency. Furthermore, the thermostats known from the prior art for the heating circuit can be completely omitted. The single control apparatus controls the operation of the entire heating apparatus.

FIG. 4 illustrates a further variant embodiment of a heating apparatus 10, which differs from the heating apparatus 10 according to FIG. 3 in that, in addition, a second energy source 30, which may be a photovoltaic installation present on site, for example, is present. The control apparatus 20 has recourse to the energy of the second energy source 30.

The second energy source 30 has an inverter 38 connected downstream thereof, which inverter converts the direct current coming from the second energy source 30 into alternating current, wherein the inverter 38 is connected to a distributor 36 to which the first energy source 16 is also connected and which is connected to the control apparatus 20 via the first connection unit 17. Furthermore, a logic unit 34 is connected to the inverter 38, which logic unit is also referred to as solar data logger. Provided the second energy source 30 is producing enough energy, the logic unit 34 outputs a control signal via a control input 35 to the control apparatus 20. The connection is designed as potential-free contact.

In addition, an operating mode setting unit 32 is present on the control apparatus 20, which operating mode setting unit is communicatively connected to the control module 22 and via which the desired heating operating mode is set.

The operating mode setting unit 32 may be designed, for example, as a sliding switch and the heating temperature setting unit 24 may be designed, for example, as a rotary switch.

The function of the electrical heating apparatus according to FIG. 4 will be described below on the basis of the illustration of the schematic circuit diagram of FIG. 5 as concrete exemplary embodiment. The control apparatus 20 in this case is designed as a two-circuit control apparatus with PI characteristics.

In the exemplary embodiment, the control apparatus is designed for the control of a heating conductor device 12 with two heating circuits 14.1, 14.2 with different power stages, wherein the powers of the stages differ in the present exemplary embodiment in the ratio 4:7.

The two power circuits may be activated individually or together, whereupon the following heating stages result (the percentage figures relate to the maximum power controllable by the control apparatus; this is achieved when both power circuits are switched on):

stage 0:0.0% power (both power circuits switched off) stage 1:36.4% power (power circuit 1 switched on) stage 2:63.4% power (power circuit 2 switched on) stage 3:100.0% power (both power circuits switched on).

The control apparatus 20 is designed such that the maximum activatable heating stage can be limited depending on the operating mode.

Heating systems with other power stages than those described above can also be used. In particular, it is also possible to use power stages with the same powers.

In the exemplary embodiment, the temperature is controlled by measuring the actual temperature via the external temperature sensor 18 installed in the floor. The set-point value of the floor temperature is set on the control apparatus 20 via the heating temperature setting unit 24. The setting region in the case of the present exemplary embodiment is between +10° C. and +55° C.

The difference between set-point and actual temperature (control deviation) is supplied to the PI control module 22 which calculates a control output (0 to 100%) therefrom. The control output is dependent on the magnitude of the control deviation (P component) and the duration of the control deviation (I component). The greater this is and the longer it endures, the higher the control output becomes.

On the basis of the calculated control output, the heating stages are connected by the control module 22 as follows:

-   control output=0%: stage 0 -   0%<control output ≦36%: stage 1 (heating circuit 14.1 activated) -   36%<control output ≦63%: stage 2 (heating circuit 14.2 activated) -   63%<control output ≦100%: stage 3 (heating circuits 14.1 and 14.2     activated).

Owing to this type of control, the heating power is successively reduced as the set-point temperature is approached and thus an overshoot of the floor temperature above the set-point value is avoided.

The operating mode of the control apparatus 20 is set via the operating mode setting unit 32. In the present exemplary embodiment, three operating modes are possible:

1. switched off (frost protection operation), 2. operation only with renewable energy (from the second energy source 30) permissible and 3. operation with renewable energy and grid energy (second energy source 30 and first energy source 16) permissible.

The respectively set operating states are displayed in a visibly recognizable manner on the control apparatus 20.

During the frost protection operation, the set-point floor temperature is permanently set to 5° C., independently of the setting via the operating mode setting unit 32. The signal input of the logic unit 34 has no function.

In the operating state “only with renewable energy”, the setting of the heating temperature setting unit 24 is used as set-point value and the heating apparatus 10 is only switched on if the signal of the logic unit 34 is active, that is to say the second energy source 30 produces enough energy. The heating stage in this operating mode may also be limited, if necessary.

During operation “with renewable energy and grid energy”, the setting of the heating temperature setting unit 24 is also used as set-point value and the heating apparatus 10 is switched on independently of the signal of the logic unit 34. In this operating mode, too, the heating stage may be limited, if necessary.

Finally, it is still possible to set rapid heating via buttons which are not illustrated in more detail, in the case of which rapid heating a defined maximum power stage is connected, independently of the set operating mode, until the floor temperature has reached the set set-point value.

The exemplary embodiment shows a floor temperature control apparatus 20 for electrical floor heaters, which is specifically designed for heating conductors with two power stages. In addition to the basic function of underfloor heating with three heating stages (heating stage 1, heating stage 2, heating stages 1+2), the power drawn from the domestic grid (first energy source 16) by the control apparatus 20 can additionally be limited by a control input, with the result that the control apparatus 20 can be used particularly expediently in connection with a further alternative energy source 30 (for example photovoltaic installation) to optimize the intrinsic consumption for the generation of renewable energy. The desired floor temperature is set in a simple manner via the heating temperature setting unit 24 (rotary knob); the operating mode setting unit 32 (sliding switch) permits the selection of the operating mode. Independently thereof, rapid heating can be started via a button. In the exemplary embodiment, the feedback of the present operating state is done, for example, via an optical display, for example via a bi-color LED.

As illustrated in FIG. 5, in the exemplary embodiment, an inverter 38 is connected downstream of the second energy source (photovoltaic installation), which is connected to a distributor 36 via a generation meter 44 which measures the total electrical energy which has been generated by the photovoltaic installation. The distributor 36 is connected to a supply and consumption meter 42 in the direction of the first energy source (power grid), which supply and consumption meter meters the energy taken from the power grid which is necessary if no energy is supplied via the second energy source 30 (photovoltaic installation). If energy which is not required is generated by the second energy source 30, this energy output into the grid is measured by the supply meter 42. The distributor 36 in turn is connected to the control apparatus 20, which controls the two heating circuits present in the exemplary embodiment on the basis of the signals of the temperature sensor 18, the set-point temperature value set via the heating temperature setting unit 24 and the operating mode set via the operating mode setting unit 32, such that the three power stages (1/3, 2/3, 3/3) illustrated schematically in FIG. 5 are in each case activatable if necessary. The supply and consumption meter 42 is designed as a current meter/bidirectional meter and feeds the current which is generated by the second energy source 30 (photovoltaic installation) and not consumed back into the grid, provided that it is not required by the heating apparatus 10.

In the exemplary embodiment shown, the photovoltaic installation (second energy source 30) generates current through solar energy. The logic unit 34 is in constant communication with the inverter 38. Threshold values are stored in the logic unit 34, that is to say it is possible, for example, in the case of a 10 kW photovoltaic installation, to connect 3.5 kW or 8 kW consumption for the intrinsic consumption on the basis of the present feed-in power. The described two-circuit control apparatus 20 decides—in communication with the logic unit 34—whether or not heating will take place with current from the second energy source 30 (current from the photovoltaic installation).

Between the logic unit 34 and the control apparatus 20, a relay station 40 can preferably be connected which enables the simple connection of electrical consumers via a network. The user configuration can in this case take place conveniently via a web interface. Furthermore, the connection can be made directly to the device via SNMP or Syslog or integrated in its own application. With a relay station 40 such as this, it is possible to measure energy consumption which enables precise determination of the energy used. Furthermore, a multiplicity of further electrical variables can be measured and represented. 

1. An electrical heating apparatus comprising: a heating conductor device containing; a first heating circuit with a first power stage, and at least one second heating circuit with a second power stage, a heating temperature setting unit that sets a set-point temperature; a temperature sensor that measures an actual temperature; an activating device that activates the heating conductor device on the basis of the respective values of the set-point and actual temperatures; a first energy source; and a single control apparatus with a control module, said single control apparatus being designed as multistage controller, wherein the single control apparatus is connected between the first energy source and the heating conductor device, the heating temperature setting unit and the temperature sensor output their signals to the control apparatus, and the control module activates or deactivates first and second power stages individually or in combination on the basis of the difference between the set-point and actual values.
 2. The heating apparatus as claimed in claim 1, wherein the control module is designed as a PI control module, which calculates in each case a control output on the basis of a control deviation in set-point and actual temperatures, a P component of said control output being dependent on the magnitude of the control deviation and an I component of said control output being dependent on the duration of the control deviation, and said control module correspondingly actuates the individual heating circuits.
 3. The heating apparatus according to claim 2, wherein each of the power stages has an identical heating power.
 4. The heating apparatus according to claim 1, wherein the power stages have different heating powers.
 5. The heating apparatus according to claim 1, further comprising: a second electrical energy source for the power stages which is connectable to the control apparatus.
 6. The heating apparatus according to, claim 1, wherein the first energy source is a regular power grid and the second energy source is designed to be an individual alternative energy source, for instance photovoltaic installation or wind turbine.
 7. The heating apparatus according to claim 5, further comprising: a logic switching unit that is connected between the second energy source and the control apparatus, to which the logic switching unit outputs a control signal relating to the respective present energy production of the second energy source and, in the event of sufficient energy production, enables the second energy source to supply energy to the heating conductor device.
 8. The heating apparatus according to claim 5, further comprising: an operating mode switching unit that communicates with the control apparatus, wherein the operating mode switching unit is configured to set the following operating states via the control apparatus, said operating states including: first state where energy is supplied to the heating conductor device via the first energy source, second state where energy is supplied to the heating conductor device via the second energy source, and third state where energy is supplied to the heating conductor device by a combination of the first and second energy source.
 9. The heating apparatus according to claim 8, wherein the control apparatus is designed such that the heating conductor device is activated only when a positive signal of the logic unit is present and the second state is activated, otherwise the heating conductor device is deactivated.
 10. The heating apparatus according to claim 8, wherein the operating states further include a fourth state where frost protection is set by the operating mode switching unit, in which fourth operating state the control apparatus activates the heating conductor device when a predefined temperature is undershot, independently of the set operating state of the second energy source.
 11. The heating apparatus according to claim 1, wherein the heating conductor device has a heating conductor which has a plurality of electrically insulated heating conductors which are actuable independently of one another and have identical or different power stages.
 12. The heating apparatus as claimed in claim 11, wherein the heating conductor device is designed as one or more heating mats, and the heating conductors are provided in a meandrous arrangement.
 13. The heating apparatus according to claim 1, further comprising: a controller housing, where the control module, the heating temperature setting unit and operating mode setting unit are arranged therein.
 14. The heating apparatus according to claim 13, wherein the housing has optical display units for displaying the set set-point temperature and the set operating state.
 15. The heating apparatus according to claim 1, wherein, when the first and second heating circuits are provided, the first power stage applies approximately 33% of the total heating power and the second power stage (L2) applies approximately 66% of the total heating power.
 16. The heating apparatus as claimed in claim 15, wherein when a control output, which is calculated by the control apparatus, is approximately 33%, the first power stage is activated, when a control output is approximately between 33% to 66%, the second power stage is activated, and when a control output is between 66% and 100%, the first and second power stages are activated.
 17. The heating apparatus according to claim 1, wherein the heating conductor device further contains at least one additional heating circuit with at least one additional power stage, and the control module activates or deactivates the at least one additional power stage. 